Added solar power to our tractor storage building (pic heavy!)

[k0ua]

After checking everything out, the equipment looks fine - but the location kills the efficiency. After checking out the panel by itself "as installed", I dismounted the panel from the wall and took it to full afternoon sun and put my meter on it. It produced, pretty much, as specified in the documentation 22.35 volts open circuit & 5.77 amps dead short (docs say 22.4v @ 5.92A). The installed location pretty much robs it of over 90% of its potential. The best readings, isolated in the installed location, were like 20.5v & .40 amps

Cost of conductors are too high for relocating the panel, so I'll leave it as is for now. It pretty much performs like a smart trickle charger. It does add to the battery charge, just not very quickly.

At some later point I may re-purpose the panel & charge controller elsewhere (pond pump or outdoor lighting feature?) & just start swapping out charged for discharged batteries as needed in the building.

So the word to the wise is that location trumps output capacity. I'd say you really need full sun for at least a good portion of the day to make solar worthwhile.

Nick

Do you have a chainsaw?

 

[k0ua]

That's what I was wondering. It will be south facing with full sun but I certainly don't want to have the panel end up too small.

If my calculations are right I'll be drawing 60w @ 12v which should come out to 5amps for one hour (so I think that means 5amp hours of drain on the battery per day?) so the panel would need to be able to replenish that.

so far so good on your calculations of the load, but How much full sun each day can you count on in WI? I think there will be many dark days up there, and if so do you need the lights? You have got to get ahead of the curve and store up energy during the sunny days to use on the dark ones. I am still thinking that even if you have good placement of the panel in good sunlight, you are still going to need at least a 50 watt panel to keep up.

 

[PRCWI]

so far so good on your calculations of the load, but How much full sun each day can you count on in WI? I think there will be many dark days up there, and if so do you need the lights? You have got to get ahead of the curve and store up energy during the sunny days to use on the dark ones. I am still thinking that even if you have good placement of the panel in good sunlight, you are still going to need at least a 50 watt panel to keep up.

So I found a site that lets me put in my location and tells me what my expected output would be, but the caviate is the panel is a 180W 24V panel.
That site says that In November I would get .56kWhr/day and in December it would be .53 kWhr/day. Those are the two worst months. My problem is I have no idea how to convert that to a 12v panel of different wattages.

Ok after some further investigation their site also lets me put in a 64W panel for charging 12v batteries and that says it would generate 0.15kWhr/Day of electricity.

If I am using 60W/Hour (60 watt hours per day) and I convert that to kilowatts (divide by 1000) then I will use 0.06kWhr/Day

So I would think you are correct that I would want at least a 50W panel and using a 100W panel while a small bit of overkill would give more breathing room for cloudy days etc.

Thoughts?

The site is Solar Calculator | Weather Underground

 

[nikdfish]

Watts are watts... they are the product of volts x amps, so they are directly comparable. You can get a single 200 watt 12v (nominal) panel if desired, or two 100w 12v panels run parallel for 200w @ 12v (and about 11.5 amps) or in series for 200w @ 24v (w about 5.8 amps).

Where doable, I am generally in favor of a bit of overkill ...

Nick

 

[vvanders]

But you have to remember I didn't know anything about radio and electronics until I did. We must all start somewhere. Also remember there are many things about many other subjects that you know about that I don't. We all have knowledge about something, and no one person knows it all.

There, you have just passed James Philosophy class 101.

Great philosophy indeed. As someone who's on the opposite side of the equation(plenty of EE/software knowledge, not enough tractor know-how), if you have the chance to pick someone's brain like this, take it!

Heck 90% of what I do day-to-day doesn't get above basic algebra and opens up all sorts of stuff.

 

[k0ua]

So I found a site that lets me put in my location and tells me what my expected output would be, but the caviate is the panel is a 180W 24V panel.
That site says that In November I would get .56kWhr/day and in December it would be .53 kWhr/day. Those are the two worst months. My problem is I have no idea how to convert that to a 12v panel of different wattages.

Ok after some further investigation their site also lets me put in a 64W panel for charging 12v batteries and that says it would generate 0.15kWhr/Day of electricity.

If I am using 60W/Hour (60 watt hours per day) and I convert that to kilowatts (divide by 1000) then I will use 0.06kWhr/Day

So I would think you are correct that I would want at least a 50W panel and using a 100W panel while a small bit of overkill would give more breathing room for cloudy days etc.

Thoughts?

The site is Solar Calculator | Weather Underground

I think you have it figured out. All you needed was a nudge to do the thinking and calculating. :thumbsup: Good luck with your project..

 

[PRCWI]

I think you have it figured out. All you needed was a nudge to do the thinking and calculating. :thumbsup: Good luck with your project..

Thanks for your help, I'll let you all know my results.

 

[nikdfish]

I had been playing with some numbers & thinking about the cost/return associated with a better location and using less than optimal conductors. Out of curiosity I built a roughly 65' 10 awg "extension cord" with the MC4 connectors I have on hand to empirically test some of my assumptions about performance with that much of a run. I figured even a 10% loss is no big deal since output at the current location is 95% + lower than optimal.

I removed the panel from the building & took it out by the driveway. Angle wasn't perfect and at about 2:30 PM, so shadows were starting to encroach on the area, but measured 20.9 volts & 4.9 amps directly at the panel. Hooked up the extension cord & measured at the far end, getting 20.7 volts & 4.49 amps. This is a moving target with some shadows moving in and out, but it looks like line loss is going to be no big deal. At the original location on the building, the panel was generally producing less than 0.25 amps (best seen was 0.4), so this is massively better.

Going to start roughing out a reasonable mount for the panel that won't offend the wife's sensibilities & will protect the panel from damage from lawn mowing, flying rocks, grandchildren, etc.

Nick

 

[nikdfish]

OK, this is my initial re-mount of the panel. Might go to a pole mount at a later date, but need to get the utility locator folks to mark phone & power runs before digging. It is a simple cobble-together of 1" EMT & some chain link fence & conduit hardware. The front legs were spread to the limit of the joints & hammered a couple of inches into the ground, as was the rear support, for a bit more stability before mounting the panel. The legs used for the building mount were used to set the angle on this mount, attaching to the emt with self tapping screws.

The extension line was run down the eave & then tree supported over to the panel

Here it is just coming into pretty much full sun.

Producing over 50 watts going into the battery (14.56v @ 3.46 amps) for the first time. (Note: a meter proved defective & was pulled pending the arrival of a replacement).

Even with worst case conditions, this location should not produce any less than if the panel were on the building.

Nick

 

[Garandman]

Looks to me like you could just put it on the roof of that pumphouse?

 

[nikdfish]

Looks to me like you could just put it on the roof of that pumphouse?

Actually laid it there for a bit while testing ...

Finally decided I didn't want to maybe chew up the asphalt shingles, and really needed a different orientation and angle for best results.

Nick

 

[nikdfish]

Well, for the first time since getting started with the solar panel thing, the controller is showing the slow blink on the battery status that indicates it has gone into "Float" charge status, with the battery readout sitting on 13.8v

Nick

 

[k0ua]

Well, for the first time since getting started with the solar panel thing, the controller is showing the slow blink on the battery status that indicates it has gone into "Float" charge status, with the battery readout sitting on 13.8v

Nick

Yaaay.. Now you just need another battery in parallel. Can't let free energy go to waste... store up that stuff!

 

[nikdfish]

Just for fun I ended up with 3 power meters on the wiring panel, one for panel to controller, one for controller to battery & one for battery to fuse block. This is a schematic for the layout:

Definately overkill, but I was curious how it looked at those different points.

Nick

 

[k0ua]

Just for fun I ended up with 3 power meters on the wiring panel, one for panel to controller, one for controller to battery & one for battery to fuse block. This is a schematic for the layout:

Definately overkill, but I was curious how it looked at those different points.

Nick

Pretty neat. Lets see if I can describe your schematic :

Coming from the panel, Meter 1 on its red and black leads monitors the raw voltage coming from the panel, and its blue and green leads are across the meter shunt so it monitors current flowing across the shunt by way of the voltage drop across the known resistance of the shunt. This is the raw current flowing into the Pulse Width Modulation charge controller.

Meter 2 on its red and black leads monitors the voltage coming out of the charge controller heading to the batter and again the blue and green leads are across the shunt which will monitor the charge current flowing into the battery.

Meter 3 will monitor the voltage with the battery supplying the loads and again the blue and green leads will measure the load current that the battery is supplying to the load.

Does that about cover it?

Well heck, I looked at it again, and noticed you already provided an explanation which I missed on the first look.. sorry.

 

[dragoneggs]

Pretty neat. Lets see if I can describe your schematic :

Coming from the panel, Meter 1 on its red and black leads monitors the raw voltage coming from the panel, and its blue and green leads are across the meter shunt so it monitors current flowing across the shunt by way of the voltage drop across the known resistance of the shunt. This is the raw current flowing into the Pulse Width Modulation charge controller.

Meter 2 on its red and black leads monitors the voltage coming out of the charge controller heading to the batter and again the blue and green leads are across the shunt which will monitor the charge current flowing into the battery.

Meter 3 will monitor the voltage with the battery supplying the loads and again the blue and green leads will measure the load current that the battery is supplying to the load.

Does that about cover it?

Well heck, I looked at it again, and noticed you already provided an explanation which I missed on the first look.. sorry.

this is why I changed majors in college from electrical to mechanical engineering. Actually I made it to diodes and transistors.. before I switched. :laughing:

 

[k0ua]

this is why I changed majors in college from electrical to mechanical engineering. Actually I made it to diodes and transistors.. before I switched. :laughing:

Well, in some ways meters and shunts are somewhat simpler to understand than diodes and transistors.

 

[Garandman]

this is why I changed majors in college from electrical to mechanical engineering. Actually I made it to diodes and transistors.. before I switched. :laughing:

I see what you did there....

 

[k0ua]

Now Dragon, don't try to tell us that figuring stresses on beams and that sort of thing is easier than some connections and some meters.. Differential equations make me dizzy.

 

[nikdfish]

I haven't posted a shot of the panel in it's final form yet, so here it is with the meter backlighting enabled (usually off). The three meters correspond to the drawing with #1 at the top and #3 at the bottom.

Since it looks like a decent location, I "staked" the three panel mount legs with some 3/8" rebar through holes I drilled near the bottoms.

I also set the feed line up with a counter weight (couple of bad 7ah UPS batteries) in case something (branch?) falls across the line. It should act as a shock absorber and help keep anything from getting jerked loose or broken.

Nick